1. Field of the Invention
This invention relates to poly(aryl ether) foams, and to processes for the production thereof. More particularly, this invention relates to processes which employ aqueous pristine blowing agents for the production of poly(aryl ether) foams, and the foams produced thereby.
2. Description of Related Art
U.S. Pat. No. 4,940,733 relates to the use of poly(alkylene carbonates) as foaming agents for foaming poly(aryl ethers) including modified poly(phenylene ethers). U.S. Pat. No. 4,837,251 relates to the use of a blowing agent such as boric acid to foam compositions which may comprise poly(aryl ethers). U.S. Pat. No. 4,919,992 relates to a process of converting semicrystalline polymers such as poly(aryl ethers) into novel physical forms with open cell, porous characteristics. U.S. Pat. Nos. 3,894,974 and 3,946,064 relate to the use of hydrazodicarboxylates as chemical blowing agents for poly(aryl ethers). U.S. Pat. Nos. 4,105,601 and 4,169,954 disclose the use of 3,3'-carbonylbis(organo carbazates) as blowing agents for poly(aryl ethers).
Although it would be highly desirable to produce foams from high melt temperature engineering thermoplastics such as poly(aryl ethers), it appears that prior art efforts to produce such foams have employed chemical blowing agents. These foams would be very useful for many purposes, such as structural applications, and as components of high temperature foam compositions. It would be highly desirable to be able to produce foams from poly(aryl ethers) with cheap physical blowing agents.
Recent advances in the foam art have emphasized environmental considerations related to the use of blowing agents. Of particular concern has been the use of halogenated blowing agents and their potential environmental impact. Therefore, it would be desirable to be able to produce poly(aryl ether) foams by a process which employs aqueous blowing agents.